This invention relates to air handling systems in particular devices and apparatus for blending separate airflows, for example an outside airflow and a return airflow.
A wide variety of air handling systems has been developed for providing fresh air and/or conditioned air to a building which can either be a large building having many stories or a smaller structure. Usually these air handling systems involve the use of one or more fan units to supply air to the building and also to exhaust air to atmosphere. Because of the noise that these fans create, which noise can sometimes pass through air duct systems, silencer devices have also been developed for air handling systems.
In an air handling system, it is often desirable or necessary to mix fresh air which generally comes from outside atmosphere with return air, that is air that is being drawn back from the interior of the building itself. The amount of fresh air or outside air that is used at any given time in an air handling system will often depend on outside weather conditions including particularly the temperature of the outside air. If for example the outside air is close to the desired temperature for room air within the building, then generally speaking more outside air can and will be introduced or used in the system, resulting in fresher air being circulated to the rooms of the building. However if the outside air is considerably colder or considerably warmer than the desired indoor room temperature, it will generally be desirable to use a greater amount of return air in the air handling system as this will result in greater economy and less demands on the heating or cooling systems of the building.
Recent U.S. Pat. No. 5,587,563 issued Dec. 24, 1996 to Yazici et al. describes an air handling system suitable for a larger building, this system including an axial fan unit mounted between inlet and outside silencers. This known system is mounted in a typical equipment room for the building and to this room can be connected inlets which supply air to the room and to the air supply equipment including the fan. Air enters the inlet silencer and is then blown by the fan through the outlet silencer which is connected to a bank of air filters. The air passes through these filters to a rectangular plenum from which the air can be taken by means of supply ducts.
In another known conventional system, the air supply equipment for the building can be mounted in an enclosed housing which can include relatively large and similar return air and supply air fans mounted within the housing and in opposite end sections thereof. The return air fan can draw return air into the housing through an inlet at one end thereof and then this return air can be exhausted to atmosphere to the desired extent or it can be passed to a central mixing chamber where outside air can be introduced through another inlet. The mixed air in this central chamber is then drawn by the supply fan through heat exchanging coil units and a filter bank and blown by the fan through an outlet located adjacent to one end of the housing. One difficulty with this conventional system however is that it must be quite long to accommodate both the supply and return air fan units in the housing and due to the need for a relatively large mixing chamber.
Another known air handling system is that taught in U.S. Pat. No. 4,605,160 issued Aug. 12, 1986 to J. L. Day. This system is mounted in a casing or housing with an axial air supply fan mounted at one end of the housing adjacent to an outlet duct. An internal partition divides the inlet end of the casing into two compartments into one of which outside air flows through one inlet and into the other of which flows return air through another inlet located in the side of the casing. Airflow from the two compartments is controlled by means of two pivoting dampers in the form of gates that extend into an air mixing region. Heat transfer coils are located on the downstream side of this air mixing region and these coils extend across the casing. The two gates can be made of insulating material and may be provided with gaskets so that they can form a seal when they are closed. One difficulty with this known system is that there is no apparent provision for exhausting return air to atmosphere after it enters the housing and before it enters into the mixing region. Another difficulty is that because only two pivoting gate dampers are used, a good mixing of the two air flows cannot be achieved before the air passes through the heat exchanging coils. This can result in inefficient use of the heat exchanging coils and also possible stratification of the air flows and coil freeze ups.
It is an object of the present invention to provide an air handling apparatus capable of blending separate airflows in an efficient manner and in a manner which does not require an excessive amount of space for the apparatus
It is a further object of the present invention to provide an air handling apparatus which is relatively inexpensive to construct and maintain and which includes both an air supply fan mounted in a housing downstream of a mixing chamber and an exhaust fan unit that is capable of exhausting a substantial portion of the return air flow, preferably up to 100% of the return air, to atmosphere.
According to one aspect of the invention an air handling apparatus for blending and conditioning separate airflows includes a housing having exterior sidewalls, a top and a bottom, and containing an interior space that includes first and second inlet chambers, an air mixing chamber, and a fan containing chamber, this housing also having a first inlet for a primary airflow opening into the first inlet chamber, a second inlet for return airflow opening into the second inlet chamber, and an air outlet connected to the fan containing chamber. There is an internal partition mounted in the housing and separating the first and second inlet chambers. A heat exchanging coil unit is mounted in the housing on a downstream side of the air mixing chamber opposite the first and second inlet chambers. A first multi-blade damper mechanism is positioned between the first inlet chamber and the air mixing chamber and is capable of adjusting the amount of the primary airflow passing from the first inlet chamber into the air mixing chamber. A second multi-blade damper mechanism is positioned between the second inlet chamber and the air mixing chamber and is capable of adjusting the amount of the return air flow passing from the second inlet chamber into the air mixing chamber. There are also provided an exhaust fan unit operatively connected to the housing and capable of removing the return air flow from the second inlet chamber and an air supply fan unit mounted in the fan-containing chamber and adapted to deliver air from the air mixing chamber to the air outlet. The first and second damper mechanisms are located at an end of the partition and are mounted on opposite sides of the partition.
Preferably the exhaust fan unit is mounted directly on top of the housing above the second inlet chamber.
According to another aspect of the invention, an air handling apparatus for blending separate airflows includes a housing having exterior or external side walls, a top and a bottom and containing an interior space having first and second inlet regions and a mixing chamber. The housing also has a first inlet for a primary airflow to pass into the first inlet region and a second inlet for a return air flow to pass into the second inlet region. There is also an air outlet located on a downstream side of the mixing chamber and away from the first and second inlet regions. An internal partition in the housing separates the first and second inlet regions. A first damper mechanism is positioned between the first inlet region and the mixing chamber and is capable of adjusting the amount of the primary airflow into the mixing chamber. This first damper mechanism comprises a first multi-blade damper and a first control mechanism for adjusting the position of the blades of the damper to open and close air gaps formed between the blades. There is also a second damper mechanism positioned between the second inlet region and the mixing chamber and capable of adjusting the amount of return air flow passing into the mixing chamber. The second damper mechanism comprises a second multi-blade damper and a second control mechanism for adjusting the position of the blades of the second damper to open and close air gaps formed between these blades. The apparatus also includes an exhaust fan unit operatively connected to the second inlet region at or near the top of the housing and selectively capable of exhausting at least a portion of the return air flow to atmosphere. Also an air supply fan unit is mounted in the housing of the downstream side of the mixing chamber and is capable of drawing air from the mixing chamber and delivering same to the air outlet.
In a preferred embodiment, the exhaust fan is mounted on top of the housing and the second inlet for the return air flow is located at a bottom end of the second inlet region. Preferably each of the first and second multi-blade dampers comprises a series of parallel, elongate damper blades with each blade having a longitudinal axis that extends substantially vertically.
According to a further aspect of the invention, an air handling apparatus for blending an outside airflow and a return airflow from a building or other structure includes a housing having two longitudinally extending sidewalls, two end walls, a top and a bottom and an air entrance section, an air mixing section and a fan section. The housing also has a first inlet for the outside airflow to enter one side of the air entrance section and a second inlet for return airflow to enter another side of the air entrance section, and an air outlet located in the fan section. First and second damper mechanisms are positioned between the air entrance section and the air mixing section and each of these damper mechanisms comprises a multi-blade damper and a control mechanism for adjusting the blade of each damper to open and close air gaps formed between the blades. The first damper mechanism is capable of controlling the outside airflow into the air mixing section and the second damper mechanism is capable of controlling the return airflow into the air mixing section. There are also provided an exhaust fan unit mounted on top of the housing above the air entrance section and selectively capable of exhausting at least a portion of the return airflow to the outside atmosphere and an air supply fan unit mounted in the fan section which is located on a side of the air mixing section opposite the air entrance section.
Preferably the side walls and the end walls of the housing are insulated with sound attenuating material. The preferred air entrance section is divided into an outside air chamber and a return air chamber by an interior partition extending from the bottom to the top of the housing.
Further features and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings.